1. Field of the Invention
This present invention relates to a transparent layer and the method for growing the same, and more particularly to a transparent layer and an improved liquid phase epitaxy method for growing the transparent layer onto a LED grown structure.
2. Description of the Prior Art
In recent years, The Light-Emitting Diode (LED) has become more and more popular. The LED has a semiconductor light generation region situated on a light absorbing substrate. The popularity with LED's is beginning to replace incandescent lamps. In order to meet the demands for light output, it is important that the overall light output efficiency of the LED be maximized. In this manner, the transparent layer plays an important role in a LED device.
In the prior art, one well-known method for growing the transparent layer in a LED device is formed by metal-organic chemical vapor deposition (MOCVD). However, there are many disadvantages in MOCVD. First, MOCVD causes a problem with environmental pollution, because the MOCVD vapor is poisonous. Furthermore, if the desired transparent layer comprises GaP or the like, there is still another safety problem with a possible explosion and spontaneous combustion of the phosphorous compound. Second, MOCVD is not an efficient method for growing the transparent layer. For example, in the case of growing a transparent layer of GaP, the growing rate is about 10 μm per hour.
Another well-known method for growing the desired transparent layer is liquid phase epitaxy (LPE). In the conventional LPE process, there are still many shortcomings and limits. A serious problem of the conventional LPE process is a melt back effect occurring in the LED top layer during the growing of the transparent layer onto the LED grown structure. The above-noted “melt back” will crack the construction of the LED device. Moreover, the uppermost layer of the LED grown structure, where the transparent layer is grown, is limited. For example, while growing a GaP onto the LED grown structure, the uppermost layer of the LED grown structure must be a lattice-matched and thick-enough layer of GaP.
Hence, it is an important object of developing an improved method for growing the transparent layer of a LED device more efficiently and optimizing the above-mentioned transparent layer.